Flexible cork compositions having a rubberlike binder and method of making the same



Patented Aug. 19, 1952 CMAKING THELSAME Jenn @WKWileYi Lancaster,'Pa., assignor to'Armration ofPennsylvani-a s'tiiong CorkCompany,

I -FLEXIBLE com; COMPOSITIONS HAVING-n ARUBBERLIKELBINDER AND METHOD/F Lancaster; Pa., acorpo =:No Drawing. Application March-19,'194;7, Serial No. 735,815

Q 6 Claims.

s. This invention relates'to corkcompositions and a I method Qof making the same. More particularly, the invention relates toffiexible cork compositions and a method of-maki'ngfcork composition having a binder of! rubber-like materia1,in which method the binder is admixed with' cork particles in the form of an-aqueousdispersion of binder such asya rubber latex and c'oagulated in the, presenceoff; the cork particles prior to molding or o sha i era s Cork compositions comprising cork particles and a suitable binder have ;been' Widely, used in various-fields in the form 'ofgaskets, liners for closures insulatiqn, shoe -products,- for example, 1;iidsoles;- nd; the like; and 7 other: similar or related-uses. fgNumerous -materials have been suggestedrior-use as abinderiorl the granulated cork. However, many of these materialslhave had certain disadvantages in: that they are not suitable for use-in the manufactureoi certain products such as closureliners as the binder portion of the composition possesses oraimp'arts a disagreeable odor to the cork; thusrendering the ---composi tion undesirable for usev ih-sealing con-' tainersfor foods; and beverages. :Other .binders are. unde i e ro z hepd n ciView ha y ai eperm eable to liquids or gases,- thus greatly reducing the-efliciency otany product to be emp1:o.yed asa:easketine-ma ia 10 r ability is desired. Still otherbinders areafiected by high temperatures, thus rendering" thecomposition unsuitable "for i use in; the;- manufacture -ofmaterials to beusedin or nearequi-pm'ent op- ;er ating at elevatedtemperatures. I Rubber-like materialshave been proposed as binders for cork composition as they possess certain characteristics which are hi hl desirable,

Gork compositions Containing rubber like binders may be employed-in the manufacture of closure liners, in the manufacture of gaskets -in the 'manuiacture of; shoe products, and in other fields in which cork compositionsare widely utilized. However; conside rable di-fficulty has been experienced in the processing oi cork composition prepared from granulated cork andrubber-like binders. For instance :when I the rubber-like {material is added in the iormofgan aqueous dispersion, such as alatex, it-has-heretofore been the practice to admi gthecork' particles .and'latex, andthereafter-mold;the mixture under such conditions as to coagulate-thelatex in the mold.

Th e jnee.,-eu e-commencesecure n ,a he he q m qsit n aini wk par and coagulated latex is eextremelydifficultto iiie i lefD e to I t e cne un e e ,2 l latex in the -composition,'iconsiderable quantities of binder are" attached .to parts of the equipment utilized in processing thematerial;

' While methods have been utilized involving the use of natural or synthetic latices as binders for fibrous materials, in "which methods the latices are at least partially coagulated prior to admixture with fibrous'.materials, sucha procedure is unsuitable for use 'in the *manufacture of cork compositions inthat'precoagulationbev fore mixing .results in a weak product. Cork compositions prepared fromgranulated cork and latices which have been coagulatedbefore admixture with the cork, ,upon visualexamination, show comparatively large rubber spots throughout the composition, thus indicating that the precoagulat'e'd rubberis'not uniformlyidistributed over the co'rk'pa'rticles; thereby resulting in a product having comparativelyfweak portions which cause rapid failure in service. 7

It is, accordingly, anlobject ofthis. invention to provide a" method of making. of improved'fiexibility.

"It is a further object of. this'invention to provide a method of making aflexible' cork composition Which method, isfcapabl'e of producing a composition oi predetermined ai permeability.

. .Still another object of this'invention is the. provisionof amethod of makingjcork composition 'tvhich' method may beipracticd at. low cost.

A further object of this, invention isthe provision of a rapid method of, making cork composition which, ii'iay bei practiced. "in" conventional equipment. I

'These and other objects of this. invention will becomeapparent to those skilled in the art upon becoming familiar withthe' following description.

I have found'that' corkcompositions having a rubber binder-and characterizedby high strength, good' flexibility, tear resistance, and, if desired, excellent. air permeabilityg'ma y be prepared by a method which includesff compounding .a rubber latex with .iiulcanizingljagents and,, other" ingredients Whicli'may vary'dependingupon the final properties desired, adding the resulting. mixture to. granulated cork in a suitable, mixing device and miringthe resulting mixture of cork and com-pounded l'atexunder conditions such that. the cork particles are'evenlyjcoatedwith the rubber and the'. .rubber is coagulatled,v and thereafter, moldin the mixture of; cork particles and coagulated rubber undergheat and pressure .for. addesired period lofjtimewvhioh s-summer; to cure thebinder. j I h k The. latices which .may belemployedin the cork composition thetic rubbers such as butadiene-styrene copolya a H 35 ployed and-"the 'thickness of tlieQ artiele being 3 practice of my invention may be a natural rubber latex, artificial dispersions of natural rubber, or may be the various synthetic rubber latices known to the art. Thus, latices of butadiene polymers; for example, polybutadiene, copolymers of butadiene and styrene (known as GR-S, and Buna S), and copolymers of butadiene and acrylonitrile (known as Hycar, Chemigum,

and Perbunan), may be..employed, as binders.

ther Lagitati on, .coagulates.

Other rubber-like materials/which may be .uti-,. lized include polymers obtained from substituted butadienes, such as chloroprene, a chlorinated butadiene. Chloroprene polymers are known to the art as neoprene. fore, the term a rubber or its equivalent, as

used herein, is intended to include natural rubber By the term synthetic and synthetic rubber. rubber is meant those synthetic substances which are commonly referred to as synthetic rubbers and which .have physical properties resembling those of natural rubbergas set forth, for example,'in.the definition offsynthetic rubber appearing on pages 3 to 4" of the Circular C427 of the United States Department of Commerce entitled SyntheticRubbers: A Review of Their Compositions'P'roperties, and Uses by Lawrence A Wood, issued June'25f1940; and on'page 9 of Natural and Synthetic'Rubbers, by Harry L. Fisher, being Edgar Marburg Lectures of 1941 presented before the Forty-Fourth Annual Meete' ing of 'the American Society for Testing Materials. Generally. speaking, particularly advantageous results maybe obtained by utilizing synmers, butadiene-acrylonitrile copolymers, and chloroprene polymers. Such materials, in addition to being more oil resistantthannatural rubber, may be more readily admixed and coagulated from latices in the" presence of cork particles.

The ratio of rubber solids to cork particles employed in the manufacture of cork composition in accordance with the method, of my invention, may be widely varied depending, among other things, 'upon the particularproducts to be made. For instance, the ratio to be employed in the manufacture of a'gaske't. may vary .somewhat from the ratioemployed inthe manufacture of 'ashoe products However, generally'speaking, advanground cork in afsuitable mixer. While the addition of the compounded latex to the cork is taking place, the materials are advantageously agitated to obtain even coating of the cork particles and coagulation of the rubber contentof the latex. This coagulation is efiected while the mass contains considerable quantities of water which is due to the use of a latex in the mixing step. While I do not intend to be limited to any particular theory of operation advanced herein, it is believed that the cork particles absorb suflicient water from the latex to cause coagulation thereof. This is assisted by the presence of acidic material in the cork particles which tends to neutralize stabilizers present in rubber latex. .The rate of coagulation is dependent upon the compounding of the latex. It is, therefore, advantageousto test the stability of the latex prior to admixing with the cork particles. This may be done by any of a number of methods well known to the art.

Broadly speaking, there i V practice'ofmyinvention, coagulation is effected mold.

Thus, in accordance with my invention, a latex of predetermined stability is advantageously employed. The presence of vulcanizing agents, softenera fillers, and the like, in the latex com- 5 pound employedin my ,invention'regulates the rate of coagulation of thelatex; *Itis advantageous to employ a latex so compounded as to re- "main stable sufiiciently long to allow uniform distribution over the cork and which, upon furl. .lWhile thetimejrequired for the coagulation of the latextotake place may vary, depending upon ithe'particular fllatex'employed, the size of the batchpan'd-"the like, generally speaking, in the by agitatingthe.cork-latex mixture for about 2 to --10 minutes. In other words, the coagulation stepof my process is completed while the mass is wet and prior to the time it is charged into the Following-the coagulation the mass -is charged into the mold and heated at an elevated temperature' between about E220f F. (and 7 v tageously' between abo 407 F. and 260f F. 'At

5 temperatures, below floa 220? F., removal of water is difficult, whereas at temperatures above about 275 F., charri'ng'of-thecork and scorching of the rubber may occur. Heating is continued for a time sufficient to remove substantially-all of the water from the mass andf-tovulcanize the rubber binder. V While the time' required to -accomplish the desired elimination of; water {and vulcanization of- 'the bi'n'der may vary, depending, among other things- 1mm the temperature em- 40 sures may be applied-fto'the cork composition.

The pressure to be-employed-is governed by the type of article desired.- For instance, if an article of low density is to be made,"flpressures on the orderof 2 5 pounds per s uare mchtcscpounds per-square inch are generallyapplied to themass. Onthe other handfwhen hi'gh density materials are desired, pressures as -l'ii'ghjas 400 pounds per square inch may be'ieiriployed Generally-speaking, in the embodiment or {my invention in volving the removal of water in the mold, low pressures areemp'loyedrr After the 'desired peri'otl of tirrie n 'the'm'old at the desired pressure and-temperature,- the-mold is cooled by any 's'uitable'f means, and the 'final composition is removea-therefromahd'is ready for use. I Y In the molding dp ra on the" 'onclitions are advantageously adjusted s' that' 'the composition loses substantially all-of the water'content thereof,

0 therebygiving a final" product having the density desired, depending up'o r'ftheehargeaade to the mold. For all practical purptse 'the water'content of the mass is reduced re swor less.

This embodiment of mygisvneen offersa' particular advantage in that "the rise of a wet; mass results in better cohesionjof the binder, thereby producing a product havingibetter flexibility and hightensilestfihlgth; othefwordsithe iilms of binder are firmly attachedfto theicorkand to each other, thus resultingfin the preductionQof a stronger product I This ocedure is" particularlyadvantageo -the manufacture'fof low density cork comp s1-t1o ns. f wmnew' density cork compositions, ;the' -products are mere peririeame,

thus' enabling theready'rmbval of water from l the, mass .inthe mold. However. if desired, ,in the manufacture of low density compositions, the material maybe dried before packing, thereby reducing somewhat the period of time required in the mold. I I I However, when a high density Product .is desired, that is, one in which the cork particles are closely packed. water removal in the mold, such as illustrated above, is .fairly .difiicult. Thus, it may be desired ,to vremove .at least .a por'tion of the water content of the massiprior to thelmolding step. (In this embodiment ofmy invention, the {mixture containing latex, vulcanizing agent, and other ingredients is formed and then poured over the cork particles and ."agita'ted'to' obtain intimate mixing and uniform distribution over the cork particles together with .coagu'lation'of the binder while the mass is wet. "Followingthe distribu-tion and coagulation of the -latex, the J resulting massis subiected to drying. In the drying operation, all or a portion of the water may he removed as desired. Generally speaking, in this embodiment of my invention, it is advantageous to reduce the water content down .to as low' as 5% of the mass. 'The 'thusdried mass is then chargedinto the mold andheated under pressures such as apressure of 400 pounds per squareinch at an elevated temperature to obtain the final product. 7

My invention may be more readily understood by reference to the following specific examples:

Example -I A vulcanizing dispersion was formed from the Darvan (polymerized organic salts of *alkyl 'aryl 'sulfonic acids) 33 Casein 25 Ground bentonite 1'7 Ammonium hydroxide r 9 Water 541 The above ingredients were weighed andplaced in a pebble mill which was allowed to :run for 72 hours when the vulcanizing dispersion was ready tor'use. I, 7

--A light mineral oil emulsion was then .pre-

pared containing 48,5 parts water, 1.5 parts AquarexlD-(a sodium-salt of the sulfate monoesters of a mixture-of higher fatty alcohols censisti-ng-ohiefly of the lauryl and myristyl deriva: tives), and 120 .parts of light mineral oil '(Sun Light Process Oil). When preparing this mixture, water and the Aquarex D were added to a mixing'container equipped with a Lightning type mixingstirrer. The ingredients were :mixed for-3 to ,5 minutes to dissolve the Aquarex D, and the oil was'added while the mixer was running. Ten minutes additional mixing after the oil was added was sufficient to thoroughly emulsify it. V

A binder was prepared from 60% GR -S latex, the light oil emulsion, and the vulcanizing dispersion in the following proportions:

Wet Dry n v .Part: Parts-solids 60'7'GBS-#3'I:stex '84 '50 Lighten Emulsion 7.1-5. :5 Vulcaniiing Dispersion 125, 442

- equipped 'wi'tna slowis'peed sweeptype stirrer.

The stirrer was started'and the softener emulsion was ,added. After one or two minutes had elapsed, the vulcaniz'i'ng-ldi'spersion was then added slowly, and lithe .stirring'oontinued until all the ingredients'were thoroughly mixed, which took about 5 minutes. I I

Onehundred parts ofYl'Q/B'O mesh cork particles were placed in a suitable mixer and with the mixer running, 9527 parts of thewet-T-liinder were; poured over the-cork granules slowly and mixing allowed to progress for about 10 minutes at which time all of the .cork' particles were thoroughly coated with the fb'iniienfiand the latex was coagulated. p I

A charge. of theQaboVe-prepared composition was then-placed in ;a steel mold which was Dressed and locked, The ,mold was then subjected to a, temperature of .271) F. to 275 .'F,, for 12 hours, thereby reducing the water content of the mat to about 5%, and vulcanizing the rubber binder. The mold was then removed/to a cooling chamber whereitwas cooled for 21/2 hours after which the .mat was removed from the mold, ready foruse.

Other examples of compositions ,which may be prepared in accordance with the process outlining Example I are givenfbelowz Examplell Reground composition cork...v.-l-..- e..l. 0 pants l00 60% GR-s-Latx. Y 84.0 at Mincral OilEmulsio f 7.15 5.0 25% AquarexZD Soluti0n {4.0 31. 0 50% Vulcanizing Dispersion :10. 25 5.12

i I wacdmplelfl Reground composition-cork .z parts. l00

' We't D17 60% Hycar '0. RlL'atexul 1 2550 I 75.0 70% Mineral Oil Emulsio :10. .7 "7.5 25% Aquarex D Solution..- 6. ,0 .1. 5 50% Vulcanizing Dispersion l'5.'5 7572 Example IV Reground composition cork -.}perts .l00

Wet lDry 60%Neoprene Latexl'. L.- 42. 0 25.0 70% Mineral Oil Emulsion. B457 2.5 25% Aquarex D Solution '2. 0 ."5 50% Vulcanizing Dispersion 5. l2 2. .56

Example V I v Parts Reground cork-rubber composition scrap 50 Grouud'standa'rdcork 50 Wet Q Dry 60%,GRS:Latex l-. ...l.. "Q -s4.-o -50. 0 70%.Mineral QiLEmulsion. .Q 7.15 5.0 25% A'quarex 'D Solution; 4. 0 1.0 50% Vulcanizing Dispersiomfl lulnA, 10.25 p 5512 j I 7 Example VI p Ground standard cork par.ts.;io0

' Wet 5 Dry 60% Neoprene Latex- 84.1) 50.10 70% Light Mineral Oil Emulsion :10. 7 7. 5 25% AquarexD Solution. 4.10" 1J0 25%Tackifie'r Emulsion 8.40 L 2.0 5o%"Glay,Fi1lerDispersion- 20. 0 l0. 0 57%,Vulcanizing Dispersionu 1'3. 2: V 7.:5

gooisio Whilefin the above examples, 7 certain ingredientsihave been set forth in certain proportions, it'is to be understood that these are merely illustrative of my invention, and that other proportions may beemployed aswell as other ingredients. "For. instance, the mineral oil emulsion serves as a softening agent for the binder and may be replaced by other softening agents, such as soft jcoumarone-indene'resin, asphalt, rosin derivatives; for example, hydrogenated methyl abietate, natural resins, and thelike. Also, other stabilizing agents than' the Aquarex D solu: tion may be? employed; For instance, such stabilizing agents as those sold commercially under the name of Aerosols may be employed. The Aerosols are dialkyl esters of sodium sulfcsuccinic. acid; suchjas' diamyl ester of sodium sulfosuccinic acid, di butyl esterof sodium sulfosuccinic acid, dihexyl ester of sodium sulfosuccinic' acid, dioctyl "ester; of sodium sulfosuccinic acid, and the like; Another'stabilizing agent which maybe employed'is that sold under the name santomerse whichis an alkyl aryl sulfonate. Triton Re-l00,"a sodiumsaltof a con-- densed aryl sulfonic 'acid,'m ay also be employed as a stabilizing agent in the'process of my invention. Such stabilizing agents as those mentioned herein maybe classified as selected from the group consisting-of surface active sulfates and surface active sulfonates.

Generally speaking, theprocess of my invention may beeffectively carried out by employing compositions comprising 25- to 80 parts by weight of a'rubb'er in the form of latex, 2.5 to 25 parts by weight of softening agent,'.5 to parts by weight stabilizing agent, and 2.6, to 8.2 parts by weight vulcanizing agent; Such-a mixture is generally added to about 100 parts by weight cork particles and processed as described herein.

The-process of my invention'results in the production of excellent cork compositions which may be employedin a wide variety of uses in that the binder is not subject to deterioration at elevated temperatures, nor does it impart any disagreeable odor to the composition. The compositions, in addition, are flexible, and, if desired, possess high air permeability.

In regard to the flexibility of compositions prepared in accordance with my invention, a thick sample may be bent repeatedly about a mandrel the same thickness as the sample, thus indicating that the compositions may be bent to an angle of approximately 180 without break- The compositions possess an unusually high air permeability as .evidenced by tests conducted on the Gurley Densometer. This instrument and the method of using it are described on page 73 of Paper Testing Methods published 1923 by T. A. P. P. I. The air permeability tests measure the rate of passage of air through a sample of thickness clamped across a square inch opening in the device. Compositions made in accordance with my invention will pass 400 cc. of air at standard conditions of temperature in 15 to 30 seconds; whereas, other materials made by methods heretofore known, generally require 150 seconds and more to pass an equivalent quantity of air. Generally, other materials require between 200 and 500 seconds to pass 400 cc. of air through a sample or similar dimensions. 7

The process'of my invention may bereadily carried out'on existing equipment at "relatively the presence or cork particles while wet, there is 8 no difiiculty experienced'from adhesion of un coagulated latex to processing equipment, and, particularly, there is no troublesome'sticking to the mold parts such as is generally experienced in methods of manufacturing cork composition, wherein coagulation is. caused to take place in themold.

As indicated above,'products of variable/air permeability may be prepared in accordance with my invention, For instance', in the manufacture of'material for ise as'a shoe product, such 'asa midsole,in which the qualities of good flexibility and high air permeability are desired, the em-' bodiment of my invention discussed above for ob taining such qualities would, of course, be followed. Whereas, when low permeability is desired, such as is the case in the manufacture of a gasket, my methodmay be adapted to the production of a material of low air permeability which still possesses good flexibility, which is desirable.

While my invention has been described with reference to certain particular embodiments and with reference to certain specific examples, it is to be understood that the invention is not limited thereby. Therefore, changes, omissions, substitutions and/or additions may be made without departing from the spirit of the invention as defined in the appended claims which are intended to be limited only as required by the prior art.

I claim:

1. A method of making cork composition which comprises forming a mixture containing a synthetic rubber latex of the group consisting of butadiene-styrene copolymer latex, butadieneacrylonitrile copolymer latex, and chloroprene polymer latex, cork particles; and a' vulcanizing agent, said composition containing about 25 to 80 parts by weight of synthetic rubber solids and about parts by weight of cork particles, agitating the resulting mixture for about 2 to 10 minutes, thereby coagulating said synthetic rubber latex, chargingthe resulting mass to a mold, heating said mass in said mold at a temperature between'about 220 F. and 275 F. and a pressure of from about 25 pounds per square inch to about 400 pounds per square inch, and removing from said mold a mass of cork composition containing less than about 5% water. 1

2. A method of making cork composition-which comprises forming a'mixture containing asynthetic rubber latex of the group consisting of butadiene styrene' copolymerlatex, "butadien'e acrylonitrile copolyiner latex, and chloropren'e polymer index," cork' par'ticlesyand a vulcanizing agent, said composition containing about 25 to 80 parts by weight of synthetic rubber solids and about 100 parts by'weig'ht of cork particles, agitating the resulting mixture 'for about 2 tom minutes, thereby coagulating said synthetic rubber latex, charging'the'resulting mass to amold, and heating said mass in said mold at a temperature between about 220 and 275 F. and a pressure'of from about 25 pounds per square inch to about 400 pounds per square inch while reducmg the water content of the mass to less than about 5%.

3. A method of making 'c'ork composition which comprises forming a mixture containing a vulcanizing agent, a synthetic rubber latex of the group consisting of butadiene-styrene copolymer latex, butadiene-acrylonitrile copolymer latex, and chloroprene polymer latex, and cork particles, said mixture containing about 25 to 80 parts by weight of synthetic rubber solids and about 100 parts by weight of cork particles, agitating the resulting mixture for a period of about 2 to 10 minutes, thereby coagulating said latex, reducing the water content of said mass containing coagulated rubber to less than about 5%, charging the resulting material to a mold, and heating said material at a temperature between about 220 F. to 275 F. and at a pressure between about 25 pounds per square inch and about 400 pounds per square inch.

4. A method of making cork composition which comprises forming a mixture containing a butadiene-styrene copolymer latex, cork particles, and a vulcanizing agent, said composition containing about 25 to 80 parts by weight of copolymer solids and about 100 parts by weight of cork particles, agitating the resulting mixture for about 2 to minutes, thereby coagulating said butadiene-styrene copolymer latex, charging the resulting mass to a mold, heating said mass in said mold at a temperature between about 220 F. and 275 F. and a pressure of from about pounds per square inch to about 400 pounds per square inch, and removing from said mold a mass of cork composition containing less than about 5% water.

5. A method of making cork composition which comprises forming a mixture containing a butadiene-acrylonitrile copolymer latex, cork parti- 10 about 220 F. and 275 F. and a pressure of from about 25 pounds per square inch to about 400 pounds per square inch, and removing from said mold a massof cork composition containing less cles, and a vulcanizing agent, said composition than about 5% water.

6. A method of making cork composition which comprises forming a mixture containin a chloroprene polymer latex, cork particles, and a vulcanizing agent, said composition containing about 25 to parts by weight of polymer solids and about parts by weight of cork particles, agitating the resulting mixture for about 2 to 10 minutes, thereby coagulating said chloroprene polymer latex, charging the resulting mass to a mold, heating said mass in said mold at a temperature between about 220 F. and 275 F. and a pressure of from about 25 pounds per square inch to about 400 pounds per square inch, and removing from said mold a mass of cork composition containing less than about 5% water.

JOHN W. WILEY.

REFERENCES CITED UNITED STATES PATENTS Number Name Date 1,567,506 Hopkinson Dec. 29, 1925 1,591,018 Cutler July 6, 1926 1,990,937 Forbes Feb. 12,1935 2,155,429 Levin Apr. 25, 1939 2,196,407 Atkinson Apr. 9, 1940 2,279,450 Diehl Apr. 12, 1942 2,345,009 Schuh Mar. 28, 1944 2,491,715 Clayton Dec. 20, 1949 

1. A METHOD OF MAKING CORK COMPOSITION WHICH COMPRISES FORMING A MIXTURE CONTAINING A SYNTHETIC RUBBER LATEX OF THE GROUP CONSISTING OF BUTADIENE-STYRENE COPOLYMER LATEX, BUTADIENEACRYLONITRILE COPOLYMER LATEX, AND CHLOROPRENE POLYMER LATEX, CORK PARTICLES, AND A VULCANIZING AGENT, SAID COMPOSITION CONTAINING ABOUT 25 TO 80 PARTS BY WEIGHT OF SYNTHETIC RUBBER SOLIDS AND ABOUT 100 PARTS BY WEIGHT OF CORK PARTICLES, AGITATING THE RESULTING MIXTURE FOR ABOUT 2 TO 10 MINUTES, THEREBY COAGULATING SAID SYNTHETIC RUBBER LATEX, CHARGING THE RESULTING MASS TO A MOLD, HEATING SAID MASS IN SAID MOLD AT A TEMPERATURE BETWEEN ABOUT 220* F. AND 275* F. AND A PRESSURE OF FROM ABOUT 25 POUNDS PER SQUARE INCH TO ABOUT 400 POUNDS PER SQUARE INCH, AND REMOVING FROM SAID MOLD A MASS OF CORK COMPOSITION CONTAINING LESS THAN ABOUT 5% WATER. 